D enters Tiobe top 20
Ola Fosheim Grøstad
ola.fosheim.grostad at gmail.com
Sat Nov 9 11:19:08 UTC 2019
On Saturday, 9 November 2019 at 02:55:37 UTC, Doc Andrew wrote:
> It could be done in baby steps, too - maybe start with a tool
> that just shows no bad behavior occurs in a simple expression.
Add something like «assume» to the language and make the
optimizer add those to its fact database. For LLVM this should be
Then add «assume» clauses to the standard library that are
manually proven correct and also add an option to convert assume
to assert for additional unit-testing. This allows you to get
started working on the optimizer and figure out how to make good
use of the extra facts.
Also, optimizing the standard library affects all compiled
programs... so even small gains might be worthwhile.
Add ensure-statements to the language. Those will be converted to
assume-statements if you throw a switch, but display a warning
that all ensure-statements have to be proven correct by an
external verifier before compilation. Thus the entire burden has
been moved to an external tool.
This would encourage third parties to work on tools to translate
D code into verifiable code to be consumed by standard
Extension: create an online certification service that allows
library code to carry a certificate that the library code has
been verified. So that all their ensure statements can be turned
into assume without throwing a switch. Certificates can be
revoked (in case you find a bug in the verification process).
Then break all dynamic checks out as asserts by transforming the
code. So that all bounds checks turn up as asserts. Break
composite asserts into individual asserts.
Verifying individual functions:
step 1.1: use data-flow to convert as many asserts as possible
step 1.2: use an external verifier to prove others if possible
If those fail, try to do the verification at the call site:
step 2.1: create a unique copy of the function for the call site
step 2.2: use dataflow to bring additional assumed preconditions
into the called function
step 2.3: go to step 1.1
> Then show the same for entire @pure functions. From there
> someone could work up to proving that pre/post-conditions in
> @pure functions are satisfied. Then maybe go on to do
> invariants, then work up to @safe @nogc code, and so on.
Yup, start with the easy ones. Like pure functions provided as
parameters to functions that work on arrays which often. Could
even limit it to the ones used in the standard library.
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